The present disclosure relates to an image forming apparatus such as a copier, a printer, a facsimile machine, or a multifunction peripheral thereof, which utilizes an electrophotographic process. More particularly, the present disclosure relates to an image forming apparatus provided with a charge eliminating device that eliminates remaining charge on the surface of a photosensitive member through electrostatic discharge to the photosensitive member by use of a discharge member.
In an image forming apparatus using the electrophotographic process, remaining charge after transferring a toner image on a photosensitive drum (image carrier) may cause a memory image due to potential unevenness in next image formation. Therefore, before performing an electrification step, the remaining charge on the photosensitive drum is eliminated by the charge eliminating device, and then the photosensitive drum is electrostatically charged again. Thus, the surface of the photosensitive drum is uniformly charged so that occurrence of a memory image can be prevented. As a method for eliminating remaining charge, an optical charge elimination method is usually adopted, in which charge elimination is performed by optical illumination.
However, when repeating charge elimination by the optical charge elimination method, photo carriers generated inside a photosensitive layer may partially remain or be accumulated. In this case, the accumulation of photo carriers causes a malfunction that potential at the surface of the photosensitive drum is lowered. Therefore, a charge elimination method other than the optical charge elimination method is desired.
As a charge elimination method other than the optical charge elimination method, there is proposed a noncontact charge elimination method utilizing a self-discharge phenomenon. In the noncontact charge elimination method, the self-discharge phenomenon from protruding parts of bumps and dips of the discharge member to electrified charge of a target of charge elimination (member to be discharged) is utilized for eliminating remaining charge on the opposed member. For example, there is known an image forming apparatus in which an electro conductive portion including textile fabric made of electro conductive yarn is disposed to face a recording medium on a conveying path between a transfer device and a fixing device, and hence charge of the recording medium after transferring by the transfer device is eliminated in a noncontact manner.
Using this noncontact charge elimination method, remaining charge on the surface of the photosensitive drum is eliminated, so as to avoid remaining of photo carriers inside the photosensitive layer, which is caused in the optical charge elimination method. Thus, the surface potential of the photosensitive drum can be prevented from being lowered. In addition, because the charge eliminating roller does not contact with the photosensitive drum, it is possible to prevent damage to the surface of the photosensitive drum from the charge eliminating roller, abrasion of the photosensitive layer, or contamination of the charge eliminating roller due to toner or toner external additive adhered to the surface of the photosensitive drum. Thus, stable charge elimination effect can be obtained for a long period of time.